Quality of producer gas from the gasification of different feedstocks pertinent to the irish climate

Miscanthus, straw and willow from short rotation coppice are promising biofuels for Ireland. However there is relatively little experience with their gasification. This work aims at optimizing and identifying the limits of their gasification in an atmospheric air blown, bubbling fluidized bed gasifier. The technical feasibility of co-gasification with wood to overcome bed agglomeration will also be investigated. In addition, the effectiveness of a Ni catalytic tar reformer at reducing tar content has been studied. Experiments were undertaken with a circulating fluidized bed operating at equivalence ratios between 0.35 and 0.45. The fuel gasified was wood. The bed material adopted was sand. Approximately 1 % of the producer gas was fed to a Ni Monolith catalyst. The performance of the catalyst was seen to increase with reactor temperature and residence time. The tar content could be successfully reduced to levels generally seen as compatible with internal combustion engines. Equilibrium modelling, based on Gibb's free energy minimization, has been conducted to assist in planning experimental work. The fuels modelled were wood and peat. The modelling has shown that the cold gas efficiency of air gasification of wood is superior to that of peat. In order to maximize the cold gas efficiency of the process, the gasifier should be operated, when utilising air at ambient temperature, at an equivalence ratio of 0.29 for wood and 0.33 for peat. The cold gas efficiency of the process improved when the air was preheated by the hot producer gas exiting the gasifier to 600 °C.